Printing head control allowing head to strike in free flight and be positively retracted



E. HYLAN 3,330,398 OL ALLOWING HEAD TO STRIKE D BE POSITIVE/LY RETR DJuly l1, 1967 1.

PRINTING HEAD CONTR IN FREE FLIGHT AN Filed Sept. 1S, 1965 ACTE 2Sheets-Sheet l July l1, 1967 J. E. HYL. 3,330,398

oNTaoL PRINTING HEAD C ALLO G D TO STRIKE IN FREE FLIGHT AND BE POSITIVRETRACTED v Filed Sept. 13, 1965 2 Sheets-Sheet 2 INVENTOR. JOHN E.HYLAN BY r 'vzwnz f.,

V.ATTORNEY United States Patent O 3,330,398 PRINTING HEAD CONTROLALLOWING HEAD T STRIKE IN FREE FLIGHT AND BE P051- TIVELY RETRACTED JohnE. Hylan, Birmingham, Mich., assignor to Burroughs Corporation, Detroit,Mich., a corporation of Michigan Filed Sept. 13, 1965, Ser. No. 486,8462 Claims. (Cl. 197-16) This invention relates to apparatus forcontrolling the impression made by a printing element, and moreparticularly, relates to apparatus for controlling a single elementprinting head so as to be in free ight when impacting upon plural sheetsof paper and sheets of carbon paper.

Single element printing heads are low-velocity highmass printingelements having a surface containing a plurality of characters. Aselected character is indexed by positioning the printing head prior toimpacting it upon the paper through an ink-carrying ribbon. When asingle element printing head is used with a plurality of sheets of paperhaving sheets of carbon between them, the character is blurred on thecarbon copies if the printing head is impacted under a constant pressuresuch as that provided by a spring. Moreover, the printing headfrequently bounces several times unless it is restrained after printing.This also causes a blurred impression. To prevent this, it is desirableto have the printing head in free ight when it impacts on the paper andto have the printing head restrained immediately after printing on thepaper.

However, when carbons are not desired, the impact momentum is too greatif the head has been in free flight. Also, the printing head should beheld firmly when it is not being impelled in free flight towards thepaper. Accordingly, it is an object of this invention to provide animproved control for a printing element.

It is a further object of this invention to provide apparatus forimpelling a single element printing head in free flight towards thepaper upon which it is to make an impression.

It is a further object of this invention to provide simple apparatus forreducing the momentum of a printing head when carbon copies are notdesired.

It is a still further object of this invention to provide an apparatuswhich is able to drive a printing head towards the paper in free flightand is yet able to prevent repeated bouncing of the printing head uponthe paper.

It is still a further object of this invention to provide apparatus forcontrolling a printing head so as to impel it in free flight towards thepaper during the printing stroke and which is still able to hold theprinting head firmly during other portions of the printing cycle.

In accordance with the above objects, apparatus is provided having adriving means including complementary cams and complementary camfollowers, a printing element, anda control surface on the printing headassembly which control surface forms a driven mating part with thedriving means.

The complementary cam followers include a tapered slot. The controlsurface on the printing head assembly is rigidly held by this slotduring a iirst portion of the printing cycle and is loosely held in theslot during the printing stroke portion of the printing cycle. When thecam followers impel the driving means into the printing stroke portionof the printing cycle, the control surface of the printing head is heldloosely by the slot. Just before the printing head strikes the paper thecam followers dwell so that the printing head strikes the paper in freeflight, i.e., with no pressure applied to the printing head from anexternal source in the direction of the paper. After the printing headimpacts on the papers one of the surfaces of the slot in the drivingmeans catches the printv3,338,398 Patented July 11, 1967 ice ing headand moves it away from the papers 'before it has time to bounce.

If a single sheet of paper is used the printing head must move furthertowards the platen before impacting the paper. A cushioned bumper ispositioned so that the printing element hits it before hitting a singlesheet of paper. The bumper subtracts some of the energy from theprinting head to prevent it from cutting the paper. When several carbonsare desired the top paper is held further away from the platen by theother Sheets of vpaper and sheets of carbon paper so that the printinghead does not hit the cushioned bumper.

The invention and other improvements thereof will be understood betterand more completely from the following detailed description whenconsidered with reference to the accompanying drawings in which:

FIG. 1 is an elevational view of a platen, a single element printinghead, and a control for the single element printing head;

FIG. 2 is a partial front view of the driving means and its matingdriven control Surface for a single element printing head during thestroke portion of the printing cycle; and

FIG. 3 is a partial front view of a driving means and the mating controlsurface of the driven means during another portion of the printingcycle.

In FIG. 1 a single element printing head 10 is shown with solid lines asit is positioned during the stroke portion of the printing cycle andwith broken lines as it is positioned during another portion of theprinting cycle. The printing head 10 impacts through an ink ribbon 12onto papers held by a platen 14. The ribbon is held by the ribbonmechanism housing 16.

T he printing head 10 is supported by a support member or lever 18 thatis pivoted about the point 20 causing the printing head to impact uponthe platen 14. The support member 18 is rigidly attached to an abutmentor pin 22, forming a control surface, shown as a solid line in FIG. 1 asit is positioned during the stroke portion of the printing cycle and asa broken line as it is positioned during another portion of the printingcycle.

Complementary cams 24 and 26 are mounted on the common shaft 28 and aredriven together. The complementary cam follower surface 30 is mounted tobe driven by the cam 24 and the complementary cam follower surface 32 ismounted to be driven by the cam 26. The complementary cam follower orrocker 34 is pinned at 35 so as to receive rotational forces in twodirections from the cam follower surface 30 and the cam follower surface32. A slot 36 on the cam follower 34 drives the control surface of thedriven means. The slot 36 is shown as a solid line during the strokeportion of the printing cycle and as a broken line during anotherportion of the printing cycle.

A resilient bumper, preferable a neoprene rubber bumper 38 is positionedwith respect to the support member 18 so that the support member 18strikes the rubber bumper after traveling approximately 0.325" which isjust before the printing head attached to the support member 18 strikesa single sheet of paper placed upon the platen 14. If several sheets ofpaper are placed one upon the other on the platen 14, the printing head10 strikes the top sheet of paper before the shaft 18 strikes the rubberbumper 38.

The rubber bumper 38, the ribbon housing 16, the cams and cam followersare all attached to a rigid carrier 40 shown in part in FIG. 1. Thecarrier 40 is movably mounted on the shaft 42 which runs parallel to theplaten 14 so that the carrier 40 may be moved from the printing positionto printing position. This type of printing element is described morefully in Patent No. 2,879,876 to Palmer et al., issued Mar. 31, 1959.The printing head may be indexed to a particular character by themechanism described in patent application Ser. No. 319,836, now PatentNo. 3,250,464, to Caspari, filed Oct. 29, 1963, and assigned to the sameassignee as this application.

Each time the cams 24 and 26 are driven through a half cycle, the camfollower 34 impels the printing head towards the platen 14 and withdrawsthe printing head 10 from the platen 14 after it has impacted upon paperon the platen. The slot 36 of the cam follower 34 drives the pin 22during the first part of the stroke portion of the printing cycle andhesitates while the printing head and supporting member 18 move in freefiight towards the platen to impact with the papers placed upon theplaten. Then the slot 36 is reversed in direction by the cam follower 34to catch the pin 22 and pull the printing head away from the platen. Ifthere is only one sheet of paper on the platen 14, the supporting member18 hits the rubber bumper 38 before the printing head hits the singlesheet of paper on the platen 14. When the slot 36 in the cam follower 34is pulling the printing head away from the platen, the pin 22 ispositioned in the narrow portion of the slot 36 so as to be heldrigidly. Complementary cams may be designed to provide the desiredmotion bythe method described on pages 112-114 of Cams by Harold A.Rothbart, John Wiley and Sons, Inc., New York, N.'Y., 1956.

In FIG. 2 a front view is shown of the slot 36, the pin 22 .and thesupporting member 18 as they are positioned with respect to each otherduring the stroke portion of a printing cycle. During this portion of aprinting cycle, the surface 44 is in contact with the pin 22 so as todrive the supporting member 18 about its pivot point 20 in the strokeportion of the printing cycle. It will be noted that the slot 36 islarge enough at this outward portion so that there is free play betweenthe pin 22, the surface 44 and a -cam surface 46 of the slot 36. Whenthe cam follower 34 pauses under the control of the cam (not shown) thepin 22 moves towards the surface 46 in the cam slot 36 so that theprinting head (not shown) is in free` ight as it moves towards theplaten. Immediately after impact the cam follower 34 is reversed indirection Yby the cam so that the surface 46 contacts the cam pin 22 soas to pull the printing head away from the platen and the pin to the endof the slot.

In FIG. 3 a front view is shown of the slot 36, the pin 22 and the shaft18 as they are positioned with respect to each other during anotherportion of the printing cycle. When the printing head is not beingdriven towards the platen, the pin 22 is in a narrower portion of theslot 36 so that the slot 36 holds it firmly between its surfaces 44 and46. In this position there is no free play in the motion of the printinghead.

It can be seen that the control for the printing head of this inventionenables the printing head to be in free flight when it is used to printon several pages with carbon paper in between and yet controls themomentum of the printing head so that it will not cut the paper when theprinting is to be done upon onlya single sheet of paper. Even though itdrives the printing head into free ight during the stroke portion of theprinting cycle, the driving means holds the printing head firmly duringother portions of the printing cycle. Moreover, the driving meansprevents bouncing of the printing head by catching it immediately afterimpact and pulling it away from the platen.

Of course, many modifications and variations in the invention arepossible in the light of the above teachings. It is therefore to beunderstood, that Within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. What isclaimed is:

1. In a single element printing device comprising:

a platen adapted to support paper on which characters are to be typed;

a printing head having a plurality of characters upon at least onesurface and being capable of being indexed so as to select one of saidcharacters for` printing upon said paper;

a shaft rigidly connected to said printing head for controlling themotion of said printing head;

a bumper rigidly positioned with respect to said shaft so as to stop theforward motion of said shaft as said printing head approaches within thethickness of three sheets of paper of said platen;

a complementary cam follower;

a pin rigidly attached to said shaft;

said complementary cam follower having a tapered slot and beingpositioned so as to engage said pin loosely during the positions of saidshaft which are closest to said bumper and positioned so as to engagesaid pin tightly when said shaft is positioned furthest away.

from said bumper; and

cam means for driving said complementary cam follower so as to causesaid slot to drive said pin in such a direction that said printing headapproaches said platen, for causing said tapered slot to dwell justbefore said printing head impacts with said paper on said platen, andfor moving said tapered slot so as to move said pin in such a directionas to pull said printing head away from said platen immediately aftersaid printing head has impacted with said platen.

2. In a single element printing device comprising:

a platen adapted to support paper on which characters are to be typed;

a printing head having a plurality of characters upon at least onesurface and being capable of being indexed so as to select one of saidcharacters for printing upon said paper;

a shaft rigidly connected to said printing head for controlling themotion of said printing head;

a resilient bumper positioned with respect to said shaft so as toyieldingly oppose the forward motion of said shaft as said printing headapproaches said platen;

a complementary cam follower;

a pin rigidly attached to said shaft;

said complementary cam follower having a tapered slot and beingpositioned so as to engage said pin loosely during the positions of saidshaft which are closest to said bumper and positioned so as to engagesaid pin tightly when said shaft is positioned furthest away from saidbumper; and

cam means for driving said complementary cam follower so as to causesaid slot to drive said pin in such a direction that said printing headapproaches said platen, for causing said tapered slot to dwell just justbefore said printing head impacts with said paper on said platen, andfor moving said tapered slot-so as to move said pin in such a'directionas to pull said printing head away from said platen immediately aftersaid printing head has impacted with said platen.

References Cited UNITED STATES PATENTS 749,914 1/ 1904 Blickensderfer197-16 1,667,773 5/ 1928 Degener 197-17 1,755,197 4/1930 Von Reppert197-17 1,803,082 12/1943 Von Reppert 197-17 2,847,105 8/ 1958 Barkdoll197-29 3,126,823 3/1964 Benson 101-93 3,144,821 8/1964 Drejza 101-933,155,033 11/1964 Nelson et al 101-93 3,195,453 7/ 1965 Thiemann 1'01-933,233,715 2/1966 Flieg 197- -16 X 3,239,049 3/'1966 Voit 197-163,241,480 3/ 1966 Cunningham 101-93 ROBERT E. PULFREY, Primary Examiner.

E. S. BURR, .Assistant Examiner.

1. IN A SINGLE ELEMENT PRINTING DEVICE COMPRISING: A PLATEN ADAPTED TOSUPPORT PAPER ON WHICH CHARACTERS ARE TO BE TYPED; A PRINTING HEADHAVING A PLURALITY OF CHARACTERS UPON AT LEAST ONE SURFACE AND BEINGCAPABLE OF BEING INDEXED SO AS TO SELECT ONE OF SAID CHARACTERS FORPRINTING UPON SAID PAPER; A SHAFT RIGIDLY CONNECTED TO SAID PRINTINGHEAD FOR CONTROLLING THE MOTION OF SAID PRINTING HEAD; A BUMPER RIGIDLYPOSITIONED WITH RESPECT TO SAID SHAFT SO AS TO STOP THE FORWARD MOTIONOF SAID SHAFT AS SAID PRINTING HEAD APPROACHES WITHIN THE THICKNESS OFTHREE SHEETS OF PAPER OF SAID PLATEN; A COMPLEMENTARY CAM FOLLOWER; APIN RIGIDLY ATTACHED TO SAID SHAFT; SAID COMPLEMENTARY CAM FOLLOWERHAVING A TAPERED SLOT AND BEING POSITIONED SO AS TO ENGAGE SAID PINLOOSELY DURING THE POSITIONS OF SAID SHAFT WHICH ARE CLOSEST TO SAIDBUMPER AND POSITIONED SO AS TO ENGAGE SAID PIN TIGHTLY WHEN SAID SHAFTIS POSITIONED FURTHEST AWAY FROM SAID BUMPER; AND CAM MEANS FOR DRIVINGSAID COMPLEMENTARY CAM FOLLOWER SO AS TO CAUSE SAID SLOT TO DRIVE SAIDPIN IN SUCH A DIRECTION THAT SAID PRINTING HEAD APPROACHES SAID PLATEN,FOR CAUSING SAID TAPERED SLOT TO DWELL JUST BEFORE SAID PRINTING HEADIMPACTS WITH SAID PAPER ON SAID PLATEN, AND FOR MOVING SAID TAPERED SLOTSO AS TO MOVE SAID PIN IN SUCH A DIRECTION AS TO PULL SAID PRINING HEADAWAY FROM SAID PLATEN IMMEDIATELY AFTER SAID PRINTING HEAD HAS IMPACTEDWITH SAID PLATEN